The present invention relates to a suction throttle valve of a compressor for use, for example, in an automotive air conditioning system and, more particularly, to a suction throttle valve of a variable displacement compressor for reducing the vibration and noise that are due to pulsation of suction refrigerant gas.
There is generally known a variable displacement compressor for use in an automotive air conditioning system and the like, which is capable of variably controlling its displacement. Such variable displacement compressor will be referred to merely as a “compressor” hereinafter. The compressor often generates noise which is due to pulsation of suction refrigerant produced when the flow rate of suction refrigerant is low. As measures against the development of such noise, some compressors have used a suction throttle valve interposed between the suction port and the suction chamber for changing open area of its suction passage in accordance with the flow rate of suction refrigerant. Japanese Patent Application Publication No. 2000-136776 discloses a compressor having this type of suction throttle valve. In the compressor of the reference, a gas passage is formed between the suction port and the suction chamber, and a valve chamber is formed between the gas passage and the suction port. The compressor has an opening control valve whose valve body is vertically movably disposed in the valve chamber. The valve body is urged upward by a spring. The valve body of the opening control valve is moved vertically in the valve chamber thereby to control the opening of the gas passage in accordance with flow rate of refrigerant gas drawn into the suction chamber through the suction port. The valve chamber communicates with the suction chamber through a communication hole and the valve body has formed therethrough a hole.
In such a compressor, the suction port communicates with the suction chamber through the hole of the valve body, the valve chamber and the communication hole. Therefore, vacuuming of the air conditioning system including the compressor, which is performed before charging with refrigerant, can be accomplished by removing air through the suction port. Additionally the pressure in the suction chamber increases remarkably when the compressor is turned off during its operation, but the increased pressure in the suction chamber is released therefrom to the suction port through the communication hole, the valve chamber and the hole of the valve body, thus the pressure in the suction chamber being reduced.
In the compressor of the reference, however, when the flow rate of suction refrigerant is low during the operation of the compressor, part of the refrigerant flowing into the suction chamber through the suction port leaks into the valve chamber through the hole of the valve body through which the valve chamber and the suction port communicate with each other. The hole of the valve body reduces throttling effect of the valve body of the opening control valve, which causes noise due to the pulsation of suction refrigerant gas. Although the hole of the valve body may be formed with a reduced open area as measures against the development of such noise, it takes a long time to vacuum the compressor when the open area is too small. In releasing the increased pressure in the suction chamber to the suction port through the communication hole, the valve chamber and the hole of the valve body when the compressor is turned off during its operation, it takes a long time to exhaust the compressor of high-pressure fluid through the hole when the open area of the hole is too small. In the meantime, the pressure in the valve chamber increases remarkably, so that the valve body of the opening control valve is pushed against the housing of the compressor by a high load. Therefore, the housing should be made with a sufficient strength to resist the load.
The present invention, which has been made in light of the above problems, is directed to a suction throttle valve of a compressor which improves the reliability of the compressor by reducing the vibration and noise developed by pulsation of suction refrigerant during operation of the compressor, and also by securely exhausting the compressor of an internal fluid in vacuuming and also by securely releasing high-pressure fluid in a suction chamber of the compressor when the compressor is turn off during its operation.